This invention relates to the processing of logs by a saw mill and in particular to a method and apparatus for processing the logs prior to their being sent to the saw mill for cutting into commercial lumber.
Virtually all present day lumber mills operate on an in-line conveyor belt basis. Logs are placed end to end on a conveyor belt. As a log is transported by the belt, it goes through a debarker, past saws where the log is cut into sections of desired length, and then is fed into a chipping saw where the log is cut into slices of desired width. The logs carried by the conveyor belt are not necessarily of approximately the same size. Therefore, to process the logs with minimum waste, the chipping saw must be adjusted for each log. If there is a great disparity in diameter of adjacent logs, one log cannot enter the chipping saw until the preceding log has completely passed through the saw and then the saw readjusted.
It is also a common practice for the trucks hauling the logs from the forest to the mill yard to dump their loads of logs at selected locations around the yard. No attempt is normally made to process the logs to any extent until the logs are placed on a conveyor leading to the mill, as described above. Approximately 30% of the raw log material stored in a typical yard does not end up as usable lumber, but is waste material of various types. Compounding the above, the U.S. Forest Service has enacted a requirement that all tree stems at least 21/2 inches in diameter and 5 feet long must be removed from the forest. This adds to the amount of log material that cannot be turned into usable lumber.
It would therefore appear desirable to sort the logs by size and type prior to their entering the saw mill so that the processing efficiency is increased. It would also be desirable to remove scrap and other non-usable logs from the system before entering the saw mill.